If you just want to retrieve a single field from a Document, the only way to do it is to retrieve all the fields from the Document and then search it. This patch is an optimization that allows you retrieve a specific field from a document without instantiating a lot of field and string objects. This reduces our memory consumption on a per query basis by around around 20% when a lot of documents are returned.
I've added a lot of comments saying you should only call it if you only ever need one field. There's also a unit test.
Improvement
Resolved
Major
Performance optimization when retrieving a single field from a document
